Implications for human-wolf conflict due to free-roaming domestic dogs predation on deer in southern Spain:

Duarte, J., García, F. J., & Fa, J. E. (2016). Depredatory impact of free-roaming domestic dogs on Mediterranean deer in southern Spain: implications for human-wolf conflict. Folia Zoologica, 65(2).

Feral domestic dogs are efficient wild ungulate hunters in many parts of the world. This has not been confirmed in Mediterranean ecosystems. However, if feral dogs can predate upon wild Mediterranean ungulates, they can also do so upon livestock. Therefore, to more realistically understand human-wolf conflict in areas where wolves and feral dogs overlap, the possible role of the latter taking domestic prey should be considered. During a 6-month study period, we carried out daily observations of a pack of mediumsized dogs, where they were the only large-bodied carnivore capable of killing ungulates in a fenced estate in southern Spain. The estate contained sizeable populations of red deer, fallow deer and mouflons, but no livestock. We described feral dog predation patterns and depredatory impact. We found that dogs predated upon a total of 57 ungulates; fallow deer (47 %), red deer (37 %), and mouflon (16 %). Red deer adults were the least frequent prey, but dogs killed significantly more females and fawns of red and fallow deer. Mouflons were attacked indistinctly. Our results suggest that dogs in our study exhibited a kill pattern similar to Iberian wolves. Therefore, in areas where wolves and feral dogs coexist, a significant proportion of livestock predation could be falsely attributed to the wild canid. In addition, the presence of feral dogs may be a cause of risk in big game hunting estates.

Monitoring feral cats' movements at important seabird colony

Bonnaud, E., Berger, G., Zarzoso-Lacoste, D., Bourgeois, K., Palmas, P., & Vidal, É. (2015). First steps in studying cat movement behaviour through VHF tracking at a major world breeding site for the Mediterranean endemic Yelkouan shearwater. Revue d'Ecologie, 70 (12)

Cats are considered one of the most harmful invasive predators of island native species, particularly adult shearwaters, which are highly vulnerable to predation. Populations of Yelkouan shearwater, an endemic species of the Mediterranean basin with only a few large breeding colonies, are predicted to decline in response to feral or free-roaming cats. In a previous study, the impact of introduced cats on the Yelkouan shearwater population of Le Levant Island was assessed through the analysis of cat diet over a two-year period. The study showed that cats prey upon three staple species: rabbits, rats, and shearwaters, with a peak of predation on shearwaters immediately upon their arrival at colonies (prospecting period). Here, we supplement this previous work by conducting a preliminary study on the movement patterns of four free-roaming cats (three feral and one domestic) using very high frequency (VHF) tracking to analyse individual behaviour and home ranges on Le Levant Island, one of the Yelkouan shearwater’s major breeding sites. Our results show that two of the three feral cats were recorded inside and in close vicinity to the shearwater colonies, mainly during the prospecting period, while the domestic cat was never recorded inside the colonies. This suggests that some feral cats could show movement behavioural patterns linked to the shearwater presence as soon as these seabirds arrive at the colonies. The monitored domestic cat also showed a relatively small home range, while feral cats covered larger distances and with overlapping territories. Based on these preliminary results of cat movement behaviour, in addition to the previous results of cat predation, it is evident that cat impact must be reduced. This may be achieved through accurate management strategy that takes cat movement behaviour into account to avoid exhausting one of the most important breeding sites for this Mediterranean endemic species

Studying cat movement behaviour through VHF tracking on Mediterranean island

Bonnaud, E., Berger, G., Zarzoso-Lacoste, D., Bourgeois, K., Palmas, P., & Vidal, É. (2015). First steps in studying cat movement behaviour through VHF tracking at a major world breeding site for the Mediterranean endemic Yelkouan shearwater. Revue d'Écologie, 70  Sup.12

Le chat représente un des prédateurs invasifs les plus menaçants pour les espèces natives des îles et particulièrement pour les oiseaux marins adultes qui sont fortement vulnérables à la prédation. Les populations du Puffin Yelkouan, espèce endémique du bassin méditerranéen, sont réparties en quelques grandes colonies de reproduction et sont en voie de déclin, notamment du fait de l’impact des chats harets et errants. Dans une étude précédemment publiée, l’impact des chats introduits sur la population de puffins de l’île du Levant a été évalué au travers du régime alimentaire du chat sur une période de deux ans. Cette étude a mis en évidence que les chats consommaient trois proies principales : le Lapin, le Rat noir et le Puffin Yelkouan, et qu’un pic de prédation de puffins était observé dès leur arrivée sur les colonies (période de prospection). Nous avons donc cherché à compléter ce travail par une étude préliminaire visant à étudier les patrons de mouvement de quatre chats (trois chats harets et un chat domestique) via un suivi VHF (very high frequency), dans le but d’analyser leurs comportements individuels et leurs domaines vitaux sur l’île du Levant, qui est l’un des principaux sites de reproduction du Puffin Yelkouan. Nos résultats montrent que deux des trois chats harets ont été détectés dans les colonies de puffins durant les périodes de prospection et de reproduction de cet oiseau marin alors que le chat domestique n’a jamais été détecté dans ces colonies. Cela suggère que les patrons de déplacement des quatre chats suivis puissent être liés à la présence des puffins dès que ces oiseaux marins arrivent à la colonie. Les chats suivis montrent des domaines vitaux de taille relativement réduite, plus larges pour les chats harets qui couvrent de plus grandes distances, et avec des territoires chevauchants, que pour le chat domestique. Ces résultats préliminaires de patrons de déplacements, couplés aux résultats précédents de prédation du chat sur le Puffin Yelkouan, nous indiquent que l’impact du chat haret se doit d’être limité. Cet objectif doit être atteint en effectuant une stratégie de gestion efficace qui tiendrait compte des patrons de déplacements des chats afin d’éviter l’épuisement d’un des sites de reproduction les plus importants pour cette espèce de puffin endémique de Méditerranée


Cats are considered one of the most harmful invasive predators of island native species, particularly adult shearwaters, which are highly vulnerable to predation. Populations of Yelkouan shearwater, an endemic species of the Mediterranean basin with only a few large breeding colonies, are predicted to decline in response to feral or free-roaming cats. In a previous study, the impact of introduced cats on the Yelkouan shearwater population of Le Levant Island was assessed through the analysis of cat diet over a two-year period. The study showed that cats prey upon three staple species: rabbits, rats, and shearwaters, with a peak of predation on shearwaters immediately upon their arrival at colonies (prospecting period). Here, we supplement this previous work by conducting a preliminary study on the movement patterns of four free-roaming cats (three feral and one domestic) using very high frequency (VHF) tracking to analyse individual behaviour and home ranges on Le Levant Island, one of the Yelkouan shearwater’s major breeding sites. Our results show that two of the three feral cats were recorded inside and in close vicinity to the shearwater colonies, mainly during the prospecting period, while the domestic cat was never recorded inside the colonies. This suggests that some feral cats could show movement behavioural patterns linked to the shearwater presence as soon as these seabirds arrive at the colonies. The monitored domestic cat also showed a relatively small home range, while feral cats covered larger distances and with overlapping territories. Based on these preliminary results of cat movement behaviour, in addition to the previous results of cat predation, it is evident that cat impact must be reduced. This may be achieved through accurate management strategy that takes cat movement behaviour into account to avoid exhausting one of the most important breeding sites for this Mediterranean endemic species

Feeding habits of house and feral cats on small Adriatic islands

Lanszki J., Kletečki E., Trócsányi B., Mužinić J., Széles G.L. & Purger J.J. 2015  (in press) Feeding habits of house and feral cats (Felis catus) on small Adriatic islands (Croatia). North-Western Journal of Zoology (online first): art.151708

The domestic cat (Felis catus), a globally recognised invasive predator, was introduced to the Adriatic islands (Croatia), but its feeding ecology and impacts on biodiversity in this region is unknown. We studied the feeding habits of house cats living in villages and feral cats on the outskirts of villages on two small islands (Olib and Silba) by analysing faecal samples collected in the spring and autumn periods. Our hypothesis was that the feeding strategies of cats as top mammalian predators vary in different environments, due to significant dissimilarities in their food resources. We surveyed the abundance of cats and their primary food types, e.g. small mammals, birds, rabbits Oryctolagus cuniculus, and lizards. Our results suggest that house cats fed most often on birds and household food, while feral cats ate mostly small mammals and lizards. Feral cats preferred the invasive mesopredator black rat (Rattus rattus) (Ivlev’s index of preference, feral cats Ei = 0.72, house cats Ei = 0.14), suggesting that cats might have an effect on rat populations. Common rabbits had a low density and were preyed on only occasionally. In both cat groups, predation on birds was more frequent during autumn migration when bird abundance was higher, than in the spring breeding period. Both groups were food generalists but in different ways, which is a fact that should be considered in planning predator pest control on the islands.

Lack of hybridization between wild and domestic cats explained by spatial segregation

Gil-Sánchez, J. M., Jaramillo, J., & Barea-Azcón, J. M. (2015). Strong spatial segregation between wildcats and domestic cats may explain low hybridization rates on the Iberian Peninsula. Zoology.

The European wildcat (Felis silvestris silvestris) is an endangered felid impacted by genetic introgression with the domestic cat (Felis silvestris catus). The problem of hybridization has had different effects in different areas. In non-Mediterranean regions pure forms of wildcats became almost extinct, while in Mediterranean regions genetic introgression is a rare phenomenon. The study of the potential factors that prevent the gene flow in areas of lower hybridization may be key to wildcat conservation. We studied the population size and spatial segregation of wildcats and domestic cats in a typical Mediterranean area of ancient sympatry, where no evidence of hybridization had been detected by genetic studies. Camera trapping of wild-living cats and walking surveys of stray cats in villages were used for capture–recapture estimations of abundance and spatial segregation. Results showed (i) a low density of wildcats and no apparent presence of putative hybrids; (ii) a very low abundance of feral cats in spite of the widespread and large population sources of domestic cats inhabiting villages; (iii) strong spatial segregation between wildcats and domestic/feral cats; and (iv) no relationship between the size of the potential population sources and the abundance of feral cats. Hence, domestic cats were limited in their ability to become integrated into the local habitat of wildcats. Ecological barriers (habitat preferences, food limitations, intra-specific and intra-guild competition, predation) may explain the severe divergences of hybridization impact observed at a biogeographic level. This has a direct effect on key conservation strategies for wildcats (i.e., control of domestic cats).

 Read more on domestic wild feline hybridisation with domestic cat

Different cat diet between islands

Bonnaud, E., Palmas, P., Bourgeois, K., Ollier, S., Zarzoso-Lacoste, D., & Vidal, E. (2015). Island specificities matter: cat diet differs significantly between islands of a major breeding archipelago for a vulnerable endemic seabird. Biological Invasions, 1-15.

Domestic cats are one of the most widespread predators on islands worldwide and are responsible for numerous reductions and extinctions of species on islands. The three main islands of the Hyères Archipelago house one of the largest colonies of the Mediterranean endemic Yelkouan shearwater Puffinus yelkouan that has recently been up-listed by the IUCN to ‘vulnerable’. The main objectives of this study were to assess the diet of cats and to study the effect of cat predation on Yelkouan shearwater populations at the archipelago scale. The diet of cats was studied using scat analyses according to years and seasons for each island. Simultaneously, Yelkouan shearwater breeding success was monitored during a period of 8 years on Port-Cros and Porquerolles, and 3 years on Le Levant. Descriptive analyses and GLM were used to compare data gathered on each island. At the archipelago scale, cats preyed strongly upon introduced mammals and shearwaters. Surprisingly, large differences appeared in cats’ diet according to the island considered. The Yelkouan shearwater was the primary prey of cats on Le Levant, but secondary on Port-Cros and Porquerolles. Cat predation was mainly concentrated during the shearwater prospecting period, when birds arrive at the colonies and look for a mate (if they are not already paired) and a burrow before breeding. Consequently cat impact was low on shearwater breeding success. However, this study demonstrates that the cat management conducted on Port-Cros was positive for fledging success. The successful cat eradication on Port-Cros supports the need to continue working for Yelkouan shearwater conservation with Le Levant as a priority, because this is where the colonies are largest and predation on Yelkouan shearwaters is very high.

Evolution of antipredator behavior in an island lizard species: the sum of all fears?

Brock, K. M., Bednekoff, P. A., Pafilis, P., & Foufopoulos, J. (2014). Evolution of antipredator behavior in an island lizard species, Podarcis erhardii (Reptilia: Lacertidae): the sum of all fears?. Evolution.

Organisms generally have many defenses against predation yet may lack effective defenses if from populations without predators. Evolutionary theory predicts that ‘costly’ antipredator behaviors will be selected against when predation risk diminishes. We examined antipredator behaviors in Aegean wall lizards, Podarcis erhardii, across an archipelago of land-bridge islands that vary in predator diversity and period of isolation. We examined two defenses, flight initiation distance and tail autotomy. Flight initiation distance generally decreased with declining predator diversity. All predator types had distinctive effects on flight initiation distance with mammals and birds having the largest estimated effects. Rates of autotomy observed in the field were highest on predator-free islands yet laboratory-induced autotomy increased linearly with overall predator diversity. Against expectation from previous work, tail autotomy was not explained solely by the presence of vipers. Analyses of populations directly isolated from rich predator communities revealed that flight initiation distance decreased with increased duration of isolation in addition to the effects of current predator diversity, whereas tail autotomy could be explained simply by current predator diversity. Although selection against costly defenses should depend on time with reduced threats, different defenses may diminish along different trajectories even within the same predator-prey system.

Read also this

Effects of feral cats on the evolution of antipredator behavior in the Aegean wall lizard

Li, B. (2012). Effects of feral cats on the evolution of antipredator behaviors in the Aegean wall lizard Podarcis erhardii (Doctoral dissertation, University of Michigan).

Exotic predators such as feral cats (Felis catus), have been the driving force behind the extinction of many endemic species of island mammals, birds and reptiles. Island endemics appear to be exceptionally susceptible to invasive predators because of small population size and frequent lack of anti-predator defenses. The goal of this study was to determine the impacts of feral cats on the island populations of Aegean Wall lizards (Podarcis erhardii, Lacertidae) in relationship to the expression of anti-predator behaviors. I estimated lizard population densities in areas with low cat density sites (LCD) versus high cat density (HCD) sites by conducting 100-m transect along dry-stone walls, on the island of Naxos, as well as on surrounding islets (Cyclades, Greece). Degree of expression of antipredator behaviors was determined by measuring flight initiation distance (FID) and rates of tail autotomy both in the field and in the lab for six populations in HCD, LCD sites and four satellite islets without cat presence. I also staged controlled encounters with mounted cats decoys and quantified escaping responses from lizards from these populations. I found that feral cats had a strong negative effect on lizard population densities. Lizards adapted their antipredator behaviors in response to cat predation by extending their FIDs, increasing their capacity for tail autotomy, and by staying closer to refugia. In laboratory predation simulations, lizards from cat-free islets had significantly shorter FIDs than LCD site lizards and in particular than HCD site lizards. Furthermore, some unique islet behaviors, presumably evolved in response to lack of predators and to ameliorate chronic conditions of food shortage, appear to render islet lizards strongly susceptible to cat predation. These behaviors include rarely utilizing available refugia, and moving towards anything new, including cat decoys. Nonetheless, I found that repeated exposures over three trials led to significant increases in FIDs for all populations, indicating at least some behavioral plasticity. My results suggest that although lizards may adapt their antipredator behaviors to cope with introduced predators, this offers at best only partial protection, so that there remains strong concern about their survival in the face of expanding feral cat populations.


Read also this post

Study shows impact of feral cats on lizards in Greek Islands

 Male of Erhard's Wall Lizard (Podarcis erhardii) . 

Credit: Jeroen Speybroeck/Wikipedia

A team of researchers with diverse backgrounds from universities in the U.S. and Greece has conducted a study of the impact of feral cats on Aegean wall lizards living in the Cyclades (Greek islands). In their paper published in Proceedings of the Royal Society B: Biological Sciences, the team describes behavior adaptations they observed in native lizards to the presence of feral cats.

Feral cats are domestic cats that are living in the wild—reports over the past several years have implicated them in a number of extinctions and declines of other species, particularly birds. Another type of creature impacted by feral cats is lizards—cats are known to kill them whether they eat them or not. In this new study, the research team ventured to the Thera, Kea and Naxos islands in the Cyclades—where cats were introduced by humans approximately 9,500 years ago—to learn more about how the native lizards have adapted to the introduced threat.

Continue reading

Read also this post

The role of cats in the eco-epidemiology of Spotted Fever Group diseases

Segura, F., Pons, I., Miret, J., Pla, J., Ortuño, A., & Nogueras, M. M. (2014). The role of cats in the eco-epidemiology of Spotted Fever Group diseases. Parasites & Vectors, 7(1), 353.

Background

Mediterranean Spotted Fever (MSF), whose etiological agent is R. conorii, is one of the oldest described vector-borne infectious diseases. Although it is endemic in the Mediterranean area, clinical cases have also been reported in other regions. R. massiliae-Bar29 is related to MSF cases. This strain is distributed worldwide. R. conorii and R.massiliae-Bar29 are transmitted by ticks. Dogs are considered the sentinel of R. conorii infection. Cats could also be involved in their transmission. Rickettsia felis, etiological agent of Flea-borne spotted fever, is mainly transmitted by the cat flea, Ctenocephalides felis. Up to now, the role of cats in its transmission is not entirely elucidated. The aim of the study is to analyze the infection in cats by these microorganisms.

Methods

The study was undertaken in Northeastern Spain. Twenty municipalities of seven regions participated in the study. 212 cats (pets and stray cats) were analyzed. Variables surveyed were: date of collection, age, sex, municipality, source, living place, outdoor activities, health status, type of disease, contact with other animals, and ectoparasite infestation. Sera were evaluated by indirect immunofluorescence antibody assay (IFA). Molecular detection (realtime PCR and sequencing) and cultures were performed on blood samples.

Results

There were 59 (27.8%) cats seroreactive to one or more microorganisms. Considering crossreactions, the seroprevalences were 15.6%-19.5% (R. massiliae-Bar29), 1.9%-6.2% (R. conorii), and 5.2%-7.5% (R. felis). A weak association was observed between SFG seropositivity and tick infestation. Ticks found on seropositive cats were Rhipicephalus pusillus, R. sanguineus and R. turanicus. DNA of Rickettsia was detected in 23 cats. 21 of them could be sequenced. Sequences obtained were identical to those sequences of SFG rickettsiae similar to R. conorii and R. massiliae. No amplification of R. felis was obtained.

Conclusions

Cats can be infected by SFG rickettsiae and produce antibodies against them. Cats may play a role in the transmission cycle of R. conorii and R. massiliae-Bar29, although the role in the R. felis cycle needs further analysis.

Stray animal populations and public health in the South Mediterranean and Middle East

Seimenis, A., & Tabbaa, D. (2014). Stray animal populations and public health in the South Mediterranean and the Middle East regions. Veterinaria italiana,50(2), 131.

Uncontrolled urban growth in South Mediterranean and the Middle East regions involves city dwellers and stray animals (mainly dogs and cats) creating a dense and downgraded environment, in which irregular street garbage collection disposes sufficient food for survival and proliferation of stray animals. Under such conditions serious public health hazards are expected due to the increase of animal bites, the multiplication of insects and rodents vectors of different viral, bacterial, fungal and parasitic agents to which humans are exposed. Traditional national stray animal eradication programs and occasional small animals' humane elimination campaigns are insufficient to avert human and veterinary health risks when not coupled with modern technologies. In such environments, multiple foci of emerging and re-emerging zoonoses easily spread, i.e. rabies, hydatidosis, leishmaniasis and toxoplasmosis. Upgrading urban and peri-urban situations requires integrated/coordinated management programmes, in which public and animal health services as well as municipalities have a crucial role. Control and upgrading programmes should be flexible and able to adapt to the specific conditions of the given country/region. In this context, intersectoral/interprofessional collaborations and community participation are crucial for any national and regional development strategies. In this respect, a global approach considering both public health and socio-economic problems shows to be extremely adequate and effective.

Anti-cat behaviour in island reptiles

Li, B., Belasen, A., Pafilis, P., Bednekoff, P., & Foufopoulos, J. (2014). Effects of feral cats on the evolution of anti-predator behaviours in island reptiles: insights from an ancient introduction. Proceedings of the Royal Society B: Biological Sciences, 281(1788), 20140339.

Exotic predators have driven the extinction of many island species. We examined impacts of feral cats on the abundance and anti-predator behaviours of Aegean wall lizards in the Cyclades (Greece), where cats were introduced thousands of years ago. We compared populations with high and low cat density on Naxos Island and populations on surrounding islets with no cats. Cats reduced wall lizard populations by half. Lizards facing greater risk from cats stayed closer to refuges, were more likely to shed their tails in a standardized assay, and fled at greater distances when approached by either a person in the field or a mounted cat decoy in the laboratory. All populations showed phenotypic plasticity in flight initiation distance, suggesting that this feature is ancient and could have helped wall lizards survive the initial introduction of cats to the region. Lizards from islets sought shelter less frequently and often initially approached the cat decoy. These differences reflect changes since islet isolation and could render islet lizards strongly susceptible to cat predation.

Top‐predator control on islands boosts endemic prey but not mesopredator

Bonnaud, E., Zarzoso‐Lacoste, D., Bourgeois, K., Ruffino, L., Legrand, J., & Vidal, E. (2010). Top‐predator control on islands boosts endemic prey but not mesopredator. Animal conservation, 13(6), 556-567.

Introduced predators on islands are responsible for numerous native species extirpations and extinctions. Predation by cats is particularly detrimental to seabirds and cat control or eradication is generally the best option to reduce their negative impacts on native fauna. However, potential cascading effects, such as mesopredator release effect, need to be monitored after cat removal. In Port-Cros Island, a cat control campaign was undertaken to eliminate the strong and recurrent threat from feral cat predation to the small yelkouan shearwater Puffinus yelkouan population, without harming a neutered domestic cat population. To evaluate the conservation value of this campaign for an island endemic and endangered species, the diet and impact of the remaining domestic cats were studied through scat analysis and trap success. Moreover, to evaluate the recovery of the seabird population and detect any potential mesopredator release effect, shearwater and rat populations were monitored before, alongside and after the cat control. Only live traps were used, and most cats were trapped in the first year of cat eradication. The last incidence of cat predation on the yelkouan shearwater occurred the following year. The recovery of the shearwater population, occurring the first year of cat control, was mainly attributable to the settlement of new breeders in the colony. Rat population dynamics fluctuated widely but, even though the interactions between rats and shearwaters at breeding cavities increased, no evidence of rat predation on shearwaters was recorded. Thus, cat control on Port-Cros Island was a success for native species conservation, proving that such management strategy can induce an increase in the population of the endemic species, here the yelkouan shearwater, without any evidence of a mesopredator release effect.

Ancient introductions of mammals in Mediterranean islands and their implications for conservation

Gippoliti, S., & Amori, G. (2006). Ancient introductions of mammals in the Mediterranean Basin and their implications for conservation. Mammal Review,36(1), 37-48.

1 The importance of taxonomy to the determination of conservation priorities and actions is widely accepted. It should be not surprising therefore that the taxonomic treatment of mammal species that have been subject to human actions in antiquity may well influence the contemporary assessment of conservation priorities at various levels.
2 As a result of early extinctions caused by humans and protohistoric and historic introductions, we suggest that the Mediterranean Basin and its islands are particularly prone to misdirection of efforts towards biodiversity conservation.
3 The two main risks associated with the failure to use an evolutionary and palaeoecological approach to conservation efforts are (i) an underestimation of the conservation importance of distinctive continental taxa vs. the apparent endemicity of island taxa; and (ii) a serious risk for native and endemic island species when anthropochorous mammals, especially ungulates, misguidedly become the focus of conservation actions, particularly inside protected areas.
4 Urgent measures, including refinement of mammal taxonomy, the exclusion of known anthropochorous taxa from conservation lists and implementation of protective legislation, are necessary to maintain the uniqueness and richness of the Mediterranean biodiversity hotspot.

Cat predation on Yelkouan shearwater

Bonnaud, E., Bourgeois, K., Vidal, E., Legrand, J., & Le Corre, M. (2009). How can the Yelkouan shearwater survive feral cat predation? A meta-population structure as a solution?. Population ecology, 51(2), 261-270.

The Yelkouan shearwater, Puffinus yelkouan, is an endangered Mediterranean endemic species of burrowing petrel threatened by feral cats. The life-history parameters of a small population of Yelkouan shearwaters on the Mediterranean island, Port-Cros, were studied in conjunction with the diet of feral cats, to examine the birds’ vulnerability to introduced cats. Yelkouan shearwaters were the birds most frequently found in cat scats, with 431 ± 72 birds killed per year, and predation highest during the pre-laying period. A demographic model was created using data for P. yelkouan and for closely related shearwater species. Without cat predation, only two of four survival rate scenarios led to a mean growth rate (λ) ≥ 1. The model was constrained to have a stable population growth rate and used to predict predation scenarios compatible with the observed population stability, because the population under study has remained stable at around 180 pairs for at least 20 years despite feral cat predation. The results of assuming that the population is closed were inconsistent with the estimated mortalities due to feral cats, while it was possible to reconcile the observed numbers of breeding pairs with the observed mortalities due to cats by assuming that Port-Cros Island is a sink sustained by immigration. This illustrates that small colonies may need to be sustained by larger ones to avoid being driven to extinction. Unfortunately, the absence of a large geographic-scale ringing program makes the precise identification of the origin of the immigrants impossible in this case.

Hyperpredation: Cat diet on a small Mediterranean island

Bonnaud, E., Bourgeois, K., Vidal, E., Kayser, Y., Tranchant, Y., & Legrand, J. (2007). Feeding ecology of a feral cat population on a small Mediterranean island. Journal of Mammalogy, 88(4), 1074-1081.

Domestic cats (Felis catus) have been introduced on many islands in the world and are responsible for much damage to native insular faunas. The worldwide success and spread of this opportunistic predator is generally associated with its trophic adaptability. We examined the diet of a long-established feral cat population on a small Mediterranean island through the analysis of 1,219 scats collected during a 4-year period. Our results confirm that feral cats are generalist predators, able to feed on a wide range of prey. However, only a few prey species formed the major part of its diet. Two introduced mammals and a Mediterranean endemic seabird provided 93% of the yearly biomass consumed by cats (ship rats, 70%; wild rabbits, 7%; and yelkouan shearwaters, 6%). Ship rats remained by far the staple prey for cats throughout the year, but the diet of feral cats was more diversified in spring and early summer, frequently including insects, reptiles, and migrant birds. Endemic yelkouan shearwaters were preyed upon most frequently in autumn and winter, that is, during the shearwaters' prelaying period. Because rats provide the majority of the food of cats, they could help to maintain or inflate this alien predator population with deleterious consequences to the endemic shearwater. A cat eradication campaign would help protect the population of shearwaters on this island.

Feral cats in Mallorca: a major reservoir of toxoplasmosis

Millán, J., Cabezón, O., Pabón, M., Dubey, J. P., & Almería, S. (2009). Seroprevalence of Toxoplasma gondii and Neospora caninum in feral cats (Felis silvestris catus) in Majorca, Balearic Islands, Spain.Veterinary parasitology, 165(3), 323-326.

Felids are important in the epidemiology of Toxoplasma gondii infection because they are the only hosts that can excrete environmentally-resistant oocysts, and there is little information of infections in truly free-living cats (Felis silvestris catus) because these cats are difficult to catch. These cats have no specific owner, are not subject of vaccination programs and do not receive prophylactic or curative treatments against parasites.

Antibodies to T. gondii assayed by the modified agglutination test (MAT) were found in 50 (84.7%) of 59 cats with a majority of cats having high MAT titers (>1:500 in 45 cats). Seroprevalence (MAT, 1:25 or more) was significantly higher in adults (94.6%) than in juveniles (<6 month old; 40.0%). Seroprevalence to N. caninum, assayed by cELISA (VMRD) and confirmed by an indirect fluorescent antibody test, was low (6.8%, 4 of 59). The prevalence of T. gondii observed in wild cats in Majorca is one of the highest reported worldwide in this species and the highest observed in Europe to date. The results suggest that feral cats in Majorca have a high rate of T. gondii infection with important implications for public health on the island since the seropositive cats are likely to have already shed T. gondii oocysts in the environment.

Cats and other predators disrupting mutualistic relationships between endemic threatened lizards and plants

Traveset, A. & N. Riera. 2005. Disruption of a plant-lizard seed dispersal system and its ecological effect on a threatened endemic plant in the Balearic Islands. Conservation Biology. 19 (2): 421-431

The introduction of exotic species to an island can have significant effects on the population density and distribution of native species and on the ecological and evolutionary interactions among them (e.g., plant-animal mutualisms). The disruption of these interactions can be dramatic, significantly reducing the reproductive success of the species and even leading to their extinction. On Menorca Island (Balearic Islands, western Mediterranean), we examined the consequences of the disruption of the mutualism between two endemic species: a perennial shrub, ( Daphne rodriguezii [Texidor]) and a frugivorous lizard (Podarcis lilfordi [Günther]). The lizard became extinct from this island (as well as from Mallorca) as a result of the introduction of carnivorous mammals, which has continued since Roman times. The relict mutualism between D. rodriguezii and the lizard currently persists only in an islet (60 ha) where P. lilfordi is still abundant. We hypothesized that the absence of this lizard from most Menorcan populations is the factor causing the regression of this plant, currently considered at risk of extinction. Through observation and experimentation in the field and laboratory, we found strong evidence that a lack of seed dispersal in Menorca is the main cause of the low seedling recruitment. First, the population with greatest seedling recruitment was that in the islet where lizards were abundant. Second, lizards appeared to be the only dispersers of D. rodriguezii. Lizards consumed large amounts of fruits, without affecting either germination or seedling growth, and moved seeds to sites suitable for plant establishment. Seedlings in Menorca, in contrast, recruited almost exclusively under the parent plants. Third, the effect of other factors that may influence plant population growth (a low fruit set and a high postdispersal seed predation) was similar between the islet and the Menorcan populations. To our knowledge, our results are the first that quantitatively show that a biological invasion can cause a disruption of a specialized plant-vertebrate mutualism that sets the plant partner on the road to extinction.

Migración e islas / Migration and islands

Islands are important stopovers for many migrant passerines. Birds arrive exahusted and with few chances to avoid predators. When these are abundant, for instance because of being well fed by domestic waste, islands become traps for birds.

Many stray cats can also kill without a need and neglect their preys. 

(foto, Gonzalo Martínez Salcedo)

Las islas son escalas fundamentales en la migración de muchas especies de paseriformes. Las aves llegan agotadas y con pocas posibilidades de reaccionar ante los depredadores. Cuando estos alcanzan densidades importantes, por tratarse de poblaciones bien alimentadas por los restos domésticos, las islas se convierten en una trampa.

Los gatos errantes también matan sin necesidad inmediata de alimentarse y abandonan sus presas.

Feral cat control benefits seabirds

Bonnaud, E., K. Bourgeois, D. Zarzoso-Lacoste & E. VidalCat impact and management on two Mediterranean sister islands: “The French conservation touch”.Pages 395-401 In: Veitch, C. R.; Clout, M. N. and Towns, D. R. (eds.). 2011.  Island invasives: eradication and management. IUCN, Gland, Switzerland.


Feral cats (Felis catus) are one of the most damaging introduced species for island species worldwide. While cat control or eradication is handled with increasing efficiency on uninhabited islands, the strong bond with humans, regardless of ownership, makes cat management difficult on inhabited islands. We conducted a cat-removal programme on Port-Cros Island where both the presence of humans and their cats threaten   Puffinus yelkouan, an endangered Mediterranean endemic species of burrowing petrel. The two largest French-breeding colonies of this procellariid are on the two studied islands: Port-Cros and Le Levant. The cat-removal programme was implemented on Port-Cros, with Le Levant used for comparison. Cat diet studied through scat analysis showed cats to be responsible for killing 162 ± 46 and 21 ± 4 shearwaters per cat and per year on Le Levant and Port-Cros respectively. Bird breeding parameters were monitored during seven years on Port-Cros (before and after cat removal) and three years on Le Levant. By constructing a shearwater population viability model, we calculated that the cat impact on the yelkouan shearwaters threatens the entire population in the long term and justified cat removal. We designed a conservation management plan for Port-Cros where, taking into account human presence, feral cats were live-trapped and domestic cats were sterilised. Following this two year campaign, cat predation of shearwaters ceased, followed by an increase in the shearwater breeding population. Thus, protecting seabirds from cat predation is possible, even on islands where inhabitants are notoriously reticent to any sort of cat removal programme.